Issues: Creating a very accurate Swing Timer

Question

In order to make SwingTimer accurate, I like the logic and example suggested by @Tony Docherty On CR. Here is the Link.

In order to highlight the given

Answer 1

Okay so I have been looking at the some code (the code I posted in your last question about Karaoke timer)

Using that code I put up some measuring system using System.nanoTime() via System.out.println() which will help us to see what is happening:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTextPane;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.text.Style;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyledDocument;

public class KaraokeTest {

    private int[] timingsArray = {1000, 1000, 9000, 1000, 1000, 1000, 1000, 1000, 1000, 1000};//word/letters timings
    private String[] individualWordsToHighlight = {" \nHello\n", " world\n", " Hello", " world", " Hello", " world", " Hello", " world", " Hello", " world"};//each individual word/letters to highlight
    private int count = 0;
    private final JTextPane jtp = new JTextPane();
    private final JButton startButton = new JButton("Start");
    private final JFrame frame = new JFrame();
    //create Arrays of individual letters and their timings
    final ArrayList chars = new ArrayList<>();
    final ArrayList charsTiming = new ArrayList<>();

    public KaraokeTest() {
        initComponents();
    }

    private void initComponents() {
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);

        for (String s : individualWordsToHighlight) {
            String tmp = jtp.getText();
            jtp.setText(tmp + s);
        }
        jtp.setEditable(false);

        startButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                startButton.setEnabled(false);
                count = 0;
                charsTiming.clear();
                chars.clear();

                for (String s : individualWordsToHighlight) {
                    for (int i = 0; i < s.length(); i++) {
                        chars.add(String.valueOf(s.charAt(i)));
                        //System.out.println(String.valueOf(s.charAt(i)));
                    }
                }

                //calculate each letters timings
                for (int x = 0; x < timingsArray.length; x++) {
                    for (int i = 0; i < individualWordsToHighlight[x].length(); i++) {
                        individualWordsToHighlight[x] = individualWordsToHighlight[x].replace("\n", " ").replace("\r", " ");//replace line breaks
                        charsTiming.add((long) (timingsArray[x] / individualWordsToHighlight[x].trim().length()));//dont count spaces
                        //System.out.println(timingsArray[x] / individualWordsToHighlight[x].length());
                    }
                }

                Timer t = new Timer(1, new AbstractAction() {
                    long startTime = 0;
                    long acum = 0;
                    long timeItTookTotal = 0;
                    long dif = 0, timeItTook = 0, timeToTake = 0;
                    int delay = 0;

                    @Override
                    public void actionPerformed(ActionEvent ae) {
                        if (count < charsTiming.size()) {

                            if (count == 0) {
                                startTime = System.nanoTime();
                                System.out.println("Started: " + startTime);
                            }

                            timeToTake = charsTiming.get(count);
                            acum += timeToTake;

                            //highlight the next word
                            highlightNextWord();

                            //System.out.println("Acum " + acum);
                            timeItTook = (acum - ((System.nanoTime() - startTime) / 1000000));
                            timeItTookTotal += timeItTook;
                            //System.out.println("Elapsed since start: " + (System.nanoTime() - startTime));
                            System.out.println("Time the char should take: " + timeToTake);
                            System.out.println("Time it took: " + timeItTook);
                            dif = (timeToTake - timeItTook);
                            System.out.println("Difference: " + dif);
                            //System.out.println("Difference2 " + (timeToTake - dif));

                            //calculate start of next letter to highlight less the difference it took between time it took and time it should actually take
                            delay = (int) (timeToTake - dif);

                            if (delay < 1) {
                                delay = 1;
                            }

                            //restart timer with new timings
                            ((Timer) ae.getSource()).setInitialDelay((int) timeToTake);//timer is usually faster thus the entire highlighting will be done too fast
                            //((Timer) ae.getSource()).setInitialDelay(delay);
                            ((Timer) ae.getSource()).restart();

                        } else {//we are at the end of the array
                            long timeStopped = System.nanoTime();
                            System.out.println("Stopped: " + timeStopped);
                            System.out.println("Time it should take in total: " + acum);
                            System.out.println("Time it took using accumulator of time taken for each letter: " + timeItTookTotal
                                    + "\nDifference: " + (acum - timeItTookTotal));
                            long timeItTookUsingNanoTime = ((timeStopped - startTime) / 1000000);
                            System.out.println("Time it took using difference (endTime-startTime): " + timeItTookUsingNanoTime
                                    + "\nDifference: " + (acum - timeItTookUsingNanoTime));
                            reset();
                            ((Timer) ae.getSource()).stop();//stop the timer
                        }
                        count++;//increment counter
                    }
                });
                t.setRepeats(false);
                t.start();
            }
        });

        frame.add(jtp, BorderLayout.CENTER);
        frame.add(startButton, BorderLayout.SOUTH);

        frame.pack();
        frame.setVisible(true);
    }

    private void reset() {
        startButton.setEnabled(true);
        jtp.setText("");
        for (String s : individualWordsToHighlight) {
            String tmp = jtp.getText();
            jtp.setText(tmp + s);
        }
        JOptionPane.showMessageDialog(frame, "Done");
    }

    private void highlightNextWord() {
        //we still have words to highlight
        int sp = 0;
        for (int i = 0; i < count + 1; i++) {//get count for number of letters in words (we add 1 because counter is only incrementd after this method is called)
            sp += 1;
        }

        while (chars.get(sp - 1).equals(" ")) {
            sp += 1;
            count++;
        }

        //highlight words
        Style style = jtp.addStyle("RED", null);
        StyleConstants.setForeground(style, Color.RED);
        ((StyledDocument) jtp.getDocument()).setCharacterAttributes(0, sp, style, true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new KaraokeTest();
            }
        });
    }
}

The output on my PC is:

Started: 10289712615974

Time the char should take: 166

Time it took: 165

Difference 1

...

Time the char should take: 166

Time it took: 155

Difference 11

...

Time the char should take: 166

Time it took: 5

Difference 161

Stopped: 10299835063084

Time it should take in total: 9960

Time it took using accumulator of time taken for each letter: 5542

Difference: 4418

Time it took using difference (endTime-startTime): 10122

Difference: -162

Thus my conclusion is the Swing Timer is actually running faster than we expect as the code in the Timers actionPerformed will not necessarily take as long as the letters expected highlighting time this of course causes an avalanche effect i.e the faster/slower the timer runs the greater/less the difference will become and timers next execution on restart(..) will take be at a different time i.e faster or slower.

in the code do this:

//calculate start of next letter to highlight less the difference it took between time it took and time it should actually take
delay = (int) (timeToTake - dif);


//restart timer with new timings
//((Timer) ae.getSource()).setInitialDelay((int)timeToTake);//timer is usually faster thus the entire highlighting will be done too fast
((Timer) ae.getSource()).setInitialDelay(delay);
((Timer) ae.getSource()).restart();

Produces a more accurate result (maximum latency Ive had is 4ms faster per letter):

Started: 10813491256556

Time the char should take: 166

Time it took: 164

Difference 2

...

Time the char should take: 166

Time it took: 164

Difference 2

...

Time the char should take: 166

Time it took: 162

Difference 4

Stopped: 10823452105363

Time it should take in total: 9960

Time it took using accumulator of time taken for each letter: 9806

Difference: 154

Time it took using difference (endTime-startTime): 9960

Difference: 0